The present invention relates generally to air conditioners, and more particularly to a system and method for controlling the outdoor fan of an air conditioner that employs a pulse width modulated compressor.
In an air conditioner, a condenser, that is, an outdoor side heat exchanger, is mounted on an outdoor unit, and serves to condense refrigerant by heat transfer to its surroundings. In such a case, the amount of heat exchange in the outdoor side heat exchanger varies with the rotational speed of a fan and an outdoor temperature. The variation in the amount of heat exchange directly affects the cooling capacity of an indoor unit.
The difference between the temperatures of refrigerant and the outdoor air is large when the outdoor temperature is relatively low, so the amount of heat exchange in the outdoor side heat exchanger is increased. Consequently, there is a concern that the evaporation temperature of refrigerant in an evaporator, that is, an indoor side heat exchanger, is decreased, and the surface of the indoor side heat exchanger may freeze. In such a case, the cooling capacity of the indoor unit is decreased.
On the other hand, the difference between the temperatures of refrigerant and the outdoor air is small when the outdoor temperature is relatively high, so the amount of heat exchange in the outdoor side heat exchanger is decreased. Consequently, the evaporation temperature of refrigerant in the indoor side heat exchanger is increased, and the amount of heat exchange of refrigerant is decreased, so the cooling capacity of the indoor unit is decreased.
Hence, in order to keep the cooling capacity of the indoor unit optimal regardless of outdoor temperature, it is necessary to properly regulate the amount of heat exchange in the outdoor side heat exchanger according to variations in outdoor temperature.
To this end, in a conventional air conditioner, the rotational speed of an outdoor fan is regulated to high speed or low speed according to outdoor temperature. This regulation is performed for not only an air conditioner having a single outdoor fan but also an air conditioner having a plurality of outdoor fans. That is, when an outdoor temperature is low, a plurality of outdoor fans are simultaneously operated at a low speed so as to reduce the amount of heat exchange in an outdoor side heat exchanger; when an outdoor temperature is high, the outdoor fans are simultaneously operated at a high speed so as to increase the amount of heat exchange in the outdoor side heat exchanger.
However, the above-described conventional method for controlling the outdoor fan of an air conditioner is problematic in that when the amount of compression and discharge of refrigerant varies with time as is the case when an inverter compressor or a pulse width modulated compressor is used, the amount of heat exchange in an outdoor side heat exchanger cannot be held constant because the outdoor fan is regulated based only on the outdoor temperature.
In particular, for a pulse width modulated compressor, the discharge of refrigerant is periodically or intermittently carried out during the operation of the compressor. That is, a loading time, during which refrigerant is discharged, and an unloading time, during which refrigerant is not discharged are alternated, so the amounts of compression and discharge of refrigerant vary with time, thereby varying the amount of refrigerant flowing through an outdoor side heat exchanger. That is, when the loading time is relatively short, the amount of refrigerant flowing through the outdoor side heat exchanger is relatively small. In this case, when the rotational speed of the outdoor fan is constant, a relatively excessive heat exchange is conducted in view of the amount of refrigerant flowing through the outdoor side heat exchanger. Accordingly, the cooling capacity of the indoor unit is increased due to the supercooling of refrigerant in the outdoor heat exchanger. On the other hand, when the loading time is relatively long, the amount of refrigerant flowing through the outdoor side heat exchanger is relatively large. In this case, when the rotational speed of the outdoor fan is constant, a relatively insufficient heat exchange is conducted in view of the amount of refrigerant flowing through the outdoor side heat exchanger. Accordingly, the cooling capacity of the indoor unit is decreased due to an increase in the condensation pressure of refrigerant in the outdoor heat exchanger.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a system and method for controlling the outdoor fan of an air conditioner employing an pulse width modulated compressor, in which the amount of heat exchange in the outdoor heat exchange of the air conditioner is properly regulated, thereby allowing the indoor unit of the air conditioner to have a proper cooling capacity.
In order to accomplish the above object, an aspect of the principles of the present invention, a system for controlling the outdoor fan of an air conditioner comprises a compressor in which the amount of discharge of refrigerant is variable during its operation; an outdoor heat exchanger connected to said compressor; an outdoor fan(s) positioned near said outdoor heat exchanger; an outdoor temperature sensor for sensing outdoor temperature; and a control unit for controlling said outdoor fan(s) to be operated in one of preset operation modes according to an outdoor temperature sensed by said outdoor temperature sensor and the amount of discharge of refrigerant of said compressor.
Further, according to another aspect of the principles of the present invention, a method for controlling the outdoor fan(s) of an air conditioner having a compressor controlled in a pulse width modulation manner comprises detecting an outdoor temperature; detecting a loading time of said compressor; and operating said outdoor fan(s) in one of preset operation modes according to a detected outdoor temperature and a detected loading time of said compressor.